1. Field of the Invention
The present invention relates to an air bag apparatus which expands a bag body on the lateral side of an occupant when a vehicle decelerates rapidly.
2. Description of the Related Art
In an air bag apparatus, a peripheral edge of an opening portion of a bag body is secured to a metallic base by rivets or the like. An inflator passing through the metal base is provided with a gas injection portion which is arranged in the opening portion of the bag body.
When a vehicle rapidly decelerates, gas is injected from the gas injection portion of the inflator so that the bag body can expands by pressure caused by the gas toward an occupant.
Concerning the expansion of the bag body, the peripheral edge of the opening portion of the bag body is secured to the metallic plate, and extension is restricted. It is possible to freely extend a position on the outside of the opening portion with respect to the opening portion peripheral edge of the bag body. In the bag body, large load is applied to a boundary portion between the freely extending position and the restrictively extending position.
In well-known air bag apparatus, in order to reduce the load exerting on the boundary portion, a plurality of reinforcing materials are superposed at the peripheral edge of the opening portion of the bag body. Further, the plurality of reinforcing materials are sewn on the bag body at the same position (at one point) on the outside of the opening portion with respect to the opening portion peripheral edge of the bag body.
However, in the air bag apparatus, tensile strength applied to the bag body is uniformly distributed and the respective reinforcing material since the plurality of reinforcing material are sewn on the bag body at the same position (at one point) as set forth above. The tensile strength applied to the bag body is equal to 1/(N+1) of tensile strength at a time when there is no reinforcing material. Accordingly, it is not ensured that the tensile strength can be efficiently distributed by the reinforcing material.